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Mendip Quarries Strategic Resource Option

We are planning a new reservoir in the Mendip Hills so that we can keep water flowing for our customers, communities and businesses across the West Country for generations to come.

What we will be doing

The Mendip Quarries scheme will use the Quarry to create the new reservoir once current quarrying operations have been completed. Minerals will be extracted from the quarry until the end of 2040, at which point it will become available for repurposing to use as a reservoir.

The new source of water will be used to supply the customers of Wessex Water and Bournemouth Water although it could, in future, be extended to include other areas.

Development of the scheme will be overseen by the Regulators Alliance for Progressing Infrastructure Development (RAPID), a partnership of the three national water regulators, Ofwat, the Environment Agency, and the Drinking Water Inspectorate. RAPID was formed to support and accelerate the development of new water supply infrastructure to meet future water needs.

The West Country has already been classified as severely water stressed by the Environment Agency and there are important reasons why we need a new reservoir.

Without developing new ways to store water and transport it, we will face shortages in the future caused by:

  • a growing population
  • more heatwaves and droughts
  • tighter environmental regulations reducing the volume of water that can be taken from the natural environment.

The new reservoir means the West Country will become more resilient to future droughts and water shortages. It will be able to supply up to 100 megalitres (Ml/d) of water during peak demand periods around the same amount of water as it would take to fill 1,000,000 baths every day.

How will the scheme work?

Left to nature, the reservoir would fill naturally with groundwater. However, this process will be too slow for it to be used as a water source for public supply, so we propose to abstract water from the River Avon downstream of the city of Bath for storage within the old quarry until it is needed. The proposed useable storage provided by the quarry will be around 33% greater than that of the Wimbleball reservoir in Somerset which meets the daily water needs of nearly 366,000 people.

When needed, the water will be abstracted from the reservoir to be put into public supply. We are still considering two potential approaches to how the water will be moved and treated after abstraction:

  • to treat it to potable standards and store it in an underground storage tank, also known as a service reservoir
  • to treat it to non-potable standards and discharge it to Longham Lakes near Bournemouth. This would then be abstracted and treated to potable water standards at existing water treatment works supplying Bournemouth Water.

What are the benefits for the environment?

Repurposing the quarry into a reservoir means the significant environmental, social and carbon impacts of building a new dam and reservoir of equivalent size can be avoided.

Just as importantly, reclaimed quarries offer immense potential for ecological restoration and enhancement of biodiversity. They can become thriving ecosystems boosting local wildlife and having positive impacts on the environment and communities. Improving biodiversity will be a fundamental part of how we plan the scheme.

The scheme will utilise a licence with agreement from the Environment Agency to only abstract from the river at times when there are sufficient surplus flows available to minimise impacts on the river and its ecology, such as during the winter months. As well as this, current abstractions from groundwater in the upper Hampshire Avon and from the river at the lower Hampshire Avon will be reduced. This is vital as the Avon is a nationally designated SSSI (Site of Special Scientific Interest) and, along with some of its tributaries, is an internationally important SAC (Special Protection Area) for the value of its wildlife.

Timescales

2035-2040: the reservoir will be built.

2040: the reservoir will be operational.

A new reservoir at Cheddar is one of the three flagship schemes being undertaken to secure water resources across the region for generations to come.
Our Poole Transfer SRO will divert treated water from Poole’s water recycling centre (WRC) to the River Stour via a new pipeline to a new WRC.
We are working on three schemes called Strategic Resource Options (SROs). These flagship projects will ensure we secure essential water supply for the future.